The sandwich structure comprises an outer cover layer, an inner cover layer disposed opposite the outer cover layer in a thickness direction, and a core layer which, as viewed in the thickness direction, is disposed between the outer and the inner cover layers and connects them. The designations “outer cover layer” and “inner cover layer” are not in principle meant to restrict the positions of the cover layers to an inner side and an outer side, but can just as well be understood to mean “front cover layer” and “back cover layer” or “first cover layer” and “second cover layer”. The sandwich structure furthermore comprises a plurality of pins that extend between the outer cover layer and the inner cover layer, through the core layer. The outer cover layer and the inner cover layer, as well as the pins, are preferably made of a fiber or fibrous composite material, in particular CFRP or GFRP. The core layer is preferably formed from foam material, such as polymethacrylimide (PMI).
Such sandwich structures are known from the prior art, for example from WO 2012/010305 A1. The purpose of the pins therein is to prevent or stop crack formation in the core layer as well as detachment or delamination of the cover layers from the core layer. The pins are usually introduced into the core layer through needles provided for this purpose. For stability reasons and because of friction between the core layer and the needles during the introduction of the pins, the length of the needles, and thus the length of the pins, is limited to about 90 mm. This length limit of about 90 mm is related to a particular density of the material of the core layer and, in the case of a change of this density, it can also deviate considerably from about 90 mm. Because the pins must extend from one cover layer to the opposite cover layer in order to prevent detachment of the cover layers from the core layer, the thickness of the core layer, and of the entire sandwich structure, is likewise limited in this manner to a maximum of about 90 mm due to the limited length of the pins. However, because it may be necessary or advantageous to provide core thicknesses considerably greater than about 90 mm for various applications of the sandwich structure (such as, for example, in airplane construction) in which applications high shear forces must be transmitted, at present it is not readily possible to also reinforce such sandwich structures with large thicknesses with pins. In other words, it is either impossible or else extremely difficult to manufacture pin-reinforced sandwich structures that also have large core thicknesses.